System to determine a state of a valve

ABSTRACT

A valve monitoring apparatus has a system to determine a state of a valve. The system determines a fluid flow first pressure at a first location within a gas turbine engine, and a second pressure of a compressed fluid at a second location within the engine when the valve is in the first position; and compares the first and second pressures to determine the valve state. The system is arranged to command the valve to move from the first position towards a second position; determine the second pressure of the compressed fluid at the second location; compare the pressure at the second location when the valve is in the first position to the pressure at the second location when the valve has been commanded to move towards the second position; and, determine whether the valve has moved from the first position towards the second position when commanded to do so.

TECHNOLOGICAL FIELD

The present disclosure relates to a system to determine a state of avalve and valve monitoring apparatus.

BACKGROUND

The gas turbine engine is known to comprise compressor systems, thecompressor system comprising a fan and stages of rotating blades andstatic vanes known as stators, The primary purpose of the compressor isto increase the pressure of fluid through the gas turbine core, Thecompressor may then deliver this compressed fluid to the combustionsystem. Thus, ambient fluid is drawn into the compressor system, oftenat temperatures at or below freezing when subjected to cold environmentsor operation at high altitude. Anti-icing systems are used to heatvarious stages of the gas turbine engine to prevent ice from developingon compressor components.

BRIEF SUMMARY

According to a first aspect, there is provided a system to determine astate of a valve, the system comprising a controller configured to:determine a first pressure of a fluid flow at a first location within agas turbine engine; determine a second pressure of a compressed fluid ata second location within the gas turbine engine when the valve is in thefirst position; compare the first pressure and the second pressure todetermine the state of the valve; command the valve to move from thefirst position towards a second position; determine the second pressureof the compressed fluid at the second location; compare the pressure atthe second location when the valve is in the first position to thepressure at the second location when the valve has been commanded tomove towards the second position; and, determine whether the valve hasmoved from the first position towards the second position when commandedto do so.

Thus, in this way, the state of the valve may be detected as part of acheck. The system is configured to determine the state of the valve whenin the first position, so determining whether the valve is closed or atleast partially open when the valve is in the first position. The systemis also configured to determine whether the valve is closed, partiallyopen or substantially open when the valve is in the first position,depending on the sensitivity of the system.

The system may be configured to determine the state of the valve when inthe second position, so determining whether the valve is closed or atleast partially open when the valve is in the second position. Thesystem is also configured to determine whether the valve is closed,partially open or substantially open when the valve is in the secondposition, depending on the sensitivity of the system.

Thus, in this way, the state of the valve when in the first and/orsecond position may be detected as part of a valve operability check.Advantageously, the step to compare the pressure at the second locationwhen the valve is in the first position to the pressure at the secondlocation provides the ability to determine whether the valve has changedstate when commanded to do so. Thus, the system provides the ability tomonitor the both the state of the valve and the operability of the valveduring a check. Should the valve fail or stick during use or as part ofa check, the system advantageously provides the ability to determine anerror in valve operability, along with an ability to determine whetherthe valve is stuck open or stuck closed.

Optionally, the second location comprises a bleed line.

The second location may be a fluid flow. The fluid flow at the secondlocation may be contained within a recess, orifice, cylinder, channel orchamber including, for example, a bleed line. The bleed line may directa portion of fluid away from the fluid flow or compressed fluid.

Optionally, the step to compare the pressure at the second location whenthe valve is in the first position to the pressure at the secondlocation when the valve has been commanded to move towards the secondposition may comprise steps to determine a change in pressure within thebleed line.

The change in pressure within the bleed line, as detected by the sensor,may signify that the valve is changing state when commanded to do so.Monitoring the rate of change in pressure over a given time periodand/or determining whether the valve actuates within a predeterminedsuccess criterion, may advantageously allow further determination ofvalve condition. Such monitoring may be completed by a suitablecontroller or data processor located within, for example, an anti-icingsystem. Such monitoring may also be completed by any such suitablecontroller or data processor which is external to the system, and whichis capable of receiving data from the system.

Optionally, the system may be configured to declare a fault condition ifthe change in pressure within the bleed line is about zero.

The controller may be configured to monitor the pressure differencebetween readings of pressure received from the second sensor. Should thedifference in pressure readings received from the second sensor when thevalve is in the first and/or second position be close to or equal zero,or not reflect expected pressure readings, the controller may declare afault condition. A fault condition may be reported if the valve fails tochange state during use, or as part of the check. Alternatively, a faultcondition may be declared if the recorded difference in pressure isbelow a predetermined percentage or fraction of the expected differencein pressure, or if the actual pressure readings are not in accordancewith the expected readings required as part of the test. Thus, thecontroller may analyse the result and declare a fault condition if thepressure difference does not satisfy a predetermined success criterionor detection threshold.

Optionally, the system may be additionally configured to declare a faultcondition if a change in pressure difference between the pressure at thefirst location and the pressure at the second location is about zero.

Should the difference in pressure readings received from the secondsensor when the valve is in the first and/or second position change theengine's operation, zero pressure change in the bleed line could, undercertain operational conditions, represent a successful test. Anadditional or alternate test could be to declare a fault condition basedon pressure difference change between the pressure at the first locationand the pressure at the second location, providing a more robust testwhen monitoring pressure change.

Optionally, the controller may be additionally configured to measure aninitial fluid pressure at a third location within a gas turbine engine;and, determine the first pressure from the initial fluid pressure.

The first pressure may represent a derived or actual figure resultingfrom observed data. Thus, the additional step of deriving a theoreticalfirst pressure from an initial pressure reduces system complexity andthe need for additional sensors to be mounted within the gas turbineengine. Additionally, the initial fluid pressure may be representativeof any area within the gas turbine engine which is sensitive toenvironmental or ambient conditions. Such data may be representative ofconditions at entry into the gas turbine engine, allowing additionalenvironmental and/or operational sensitivity, and the ability to corrector compare data where required.

Optionally, the bleed line may be configured to extend from a compressorexit flow to a component.

The compressed fluid is removed from a flow which is sufficiently heatedto provide a heating effect to the components comprised within thesystem, without removing large amounts of power from the engine, oroverheating the components within the system. The compressor exit flowmay be an intermediate pressure compressor exit flow. The component maybe an engine section stator stage. Furthermore, the valve may beconfigured within the bleed line which may be located within the gasturbine engine. The valve may allow or prevent flow from a compressorexit flow towards the engine section stator stage when commanded to doso by the controller. The compressor exit flow may be the intermediatepressure compressor exit flow.

Optionally, the system may comprise a first sensor within a fluid flowat a first location within a gas turbine engine configured to measurethe first pressure, the first sensor being in communication with thecontroller.

The first sensor may be configured to measure an initial or firstpressure within the gas turbine engine. The first pressure may representa derived or an actual figure resulting from observed data. Theadditional step of deriving a theoretical first pressure from an initialpressure reduces system complexity and the need for additional sensorsto be mounted within the gas turbine engine.

Optionally, the system may comprise a second sensor at a second locationwithin the gas turbine engine configured to measure the pressure at thesecond location, the second sensor being in communication with thecontroller.

The second sensor may be configured to measure a second pressure withinthe gas turbine engine when the valve is in the first and/or secondposition. The first and second sensors may be in communication with thecontroller in order to analyse or determine one or more of the pressureat the first and second locations, the pressure difference, or thechange in the pressure difference between the first and second locationsduring operation. The sensors may be in electrical contact with thecontroller, or the controller may be external to the system.

Optionally, the controller may be configured to declare a faultcondition if a difference between the pressure at the second locationwhen the valve is in a first position and when the valve is in a secondposition is about zero.

Optionally, the controller may be configured to declare a faultcondition if a change in pressure difference between the pressure at thefirst location and the pressure at the second location is about zero.

Optionally, the controller may be configured to determine the firstpressure from an initial fluid pressure at a third location within thegas turbine engine.

Optionally, the bleed line may be configured to extend from a compressorexit flow to a component.

The compressor exit flow may be an intermediate pressure compressor exitflow. The component may be an engine section stator stage.

According to a second aspect, there is provided a gas turbine enginecomprising a bleed line; a valve within the bleed line to control flowtherethrough; a first pressure sensor within the gas turbine engine; asecond pressure sensor within the bleed line; and, a controllerconfigured to receive a first pressure reading from the first pressuresensor and a second pressure reading from the second pressure sensor,the controller being configured to perform the steps according to thefirst aspect.

According to a second aspect, there is provided a system to determine astate of a valve, the system comprising a controller comprising aprocessor, the processor being configured to function as a determiningmodule to make a comparison between values and: determine a firstpressure of a fluid flow at a first location within a gas turbineengine; determine a second pressure of a compressed fluid at a secondlocation within the gas turbine engine when the valve is in the firstposition; compare the first pressure and the second pressure todetermine the state of the valve; command the valve to move from thefirst position towards a second position; determine the second pressureof the compressed fluid at the second location; compare the pressure atthe second location when the valve is in the first position to thepressure at the second location when the valve has been commanded tomove towards the second position; and, determine whether the valve hasmoved from the first position towards the second position when commandedto do so.

According to a fourth aspect, there is provided a method to determine astate of a valve when the valve is in a first position, the methodcomprising steps to determine a first pressure of a fluid flow at afirst location within a gas turbine engine; determine a second pressureof a compressed fluid at a second location within the gas turbine enginewhen the valve is in the first position; compare the first pressure andthe second pressure to determine the state of the valve; command thevalve to move from the first position towards a second position;determine the second pressure of the compressed fluid at the secondlocation; compare the pressure at the second location when the valve isin the first position to the pressure at the second location when thevalve has been commanded to move towards the second position; and,determine whether the valve has moved from the first position towardsthe second position when commanded to do so.

The skilled person will appreciate that except where mutually exclusive,a feature described in relation to any one of the above aspects may beapplied mutatis mutandis to any other aspect. Furthermore except wheremutually exclusive any feature described herein may be applied to anyaspect and/or combined with any other feature described herein.

BRIEF DESCRIPTION

Embodiments will now be described by way of example only, with referenceto the Figures, in which:

FIG. 1 illustrates a cross-sectional side view of a gas turbine engineaccording to various examples;

FIG. 2 illustrates a cross-sectional side view of a gas turbine engineaccording to various examples;

FIG. 3 illustrates a chart showing second pressure of fluid within ableed line against state of the valve according to various examples;

FIG. 4 illustrates a chart showing second pressure of fluid within ableed line against compressor entry pressure; and,

FIG. 5 illustrates a process according to various examples,

DETAILED DESCRIPTION

In the following description, the terms ‘connected’ and ‘coupled’ meanoperationally connected and coupled. It should be appreciated that theremay be any number of intervening components between the mentionedfeatures, including no intervening components.

With reference to FIG. 1, a gas turbine engine is generally indicated at10, having a principal and rotational axis 11. The engine 10 comprises,in axial flow series, a fluid intake 12, a propulsive fan 13, anintermediate pressure compressor 14, a high-pressure compressor 15,combustion equipment 16, a high-pressure turbine 17, an intermediatepressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20.A nacelle 21 generally surrounds the engine 10 and defines both theintake 12 and the exhaust nozzle 20.

The engine 10 works in the conventional manner so that fluid enteringthe intake 12 is accelerated by the fan 13 to produce two fluid flows: afirst fluid flow into the intermediate pressure compressor 14 and asecond fluid flow which passes through a bypass duct 22 to providepropulsive thrust. The intermediate pressure compressor 14 compressesthe fluid flow directed into it before delivering that fluid to the highpressure compressor 15 where further compression takes place. In thedescribed example of an engine 10, the fluid 64 is air. In furtherexamples, the fluid can vary in composition according to specific useand environment.

The compressed fluid exhausted from the high-pressure compressor 15 isdirected into the combustion equipment 16 where it is mixed with fueland the mixture combusted, The resultant hot combustion products thenexpand through, and thereby drive the high, intermediate andlow-pressure turbines 17, 18, 19 before being exhausted through thenozzle 20 to provide additional propulsive thrust. The high 17,intermediate 18 and low 19 pressure turbines drive respectively the highpressure compressor 15, intermediate pressure compressor 14 and fan 13,each by suitable interconnecting shaft. The operation of the engine 10,inclusive of the delivery of fuel and combustion thereof, are controlledby electronic engine control apparatus 31.

Other engines 10 to which the present disclosure could be applied couldhave alternative configurations. Such engines may have an alternativenumber of interconnecting shafts (e.g. two) and/or an alternative numberof compressors and/or turbines. Further the engine may comprise agearbox provided in the drive train from a turbine to a compressorand/or fan.

Some engines 10 include anti-icing functions designed to prevent ormitigate/reduce ice formation due to water droplets freezing on one ormore component surfaces either before or after operation. Suchcomponents include, for example, the intermediate pressure compressor 14and engine section stators 22 located towards the cooler frontal regionsof the engine 10. In situations where ice formation is likely to occur,for example, during cold ambient or operating conditions, cruise ordescent of the aircraft, a supply of anti-icing fluid to the component62 may be activated to warm the component 62 and either melt thedeveloped ice, or prevent its further formation. Such anti-icingfunctions protect the engine core in situations where ice is likely toaccrete by preventing ice from being drawn into the engine 10. Supply ofanti-icing fluid 64 to the component 62 is activated, for example,following a change in operational conditions which result in anincreased potential for ice formation. Such changes may include engine10 inlet temperatures, engine or power rating, altitude, ambienttemperature/conditions, and speed relative to one or more of the groundand the air.

FIG. 2 shows a schematic diagram of an anti-icing system 23 configuredto provide a pressurised and/or heated fluid 64 to a component 62 byremoving fluid 64 from a fluid flow. FIG. 2 shows P20 pressure towardsthe front of the engine 10 describing low pressure compressor 13 inlettotal pressure also termed fan entry pressure, P21 pressure describingfan root delivery pressure, P24 pressure showing intermediate pressurecompressor 14 inlet total pressure, and P26 pressure showing highpressure compressor 15 inlet total pressure, which depending on engineconfiguration, is often approximately equivalent to intermediatepressure compressor 14 exit pressure. Additionally, FIG. 2 shows theintermediate pressure compressor 14 stage, the engine section stator 22and high pressure compressor 15 stages, and their relation to pressuresP20, P21, P24 and P26.

In the example shown in FIG. 2, the fluid 64 is compressed and heated bypassing through one or more compression stages. The fluid 64 is divertedfrom a region between the intermediate pressure compressor 14 outlet andhigh pressure compressor 15 inlet. However, sufficiently compressedand/or heated fluid 64 can alternatively be diverted from one or morefurther locations within the engine 10. FIG. 2 also shows that the fluid64, once removed from the fluid flow, is fed into a component 62.

The fluid 64 is fed into the component 62 via a bleed line 60. In somearrangements, a manifold 61 is additionally attached to the bleed line60 between two or more components 62 and the bleed line 60. The manifold61, if attached to the bleed line 60, serves to provide the bleed line60 with two or more outlets so that the fluid 64 can flow into two ormore components 62 susceptible to ice formation located within oradjacent to the gas turbine engine 10.

As shown in FIG. 2, the system includes a controller 24. In someexamples, controller 24 may e a module. As used herein, the working‘module’ refers to a device or apparatus where one or more features areincluded at a later time and, possibly, by another manufacturer or by anend user. The controller 24 may comprise any suitable circuitry to causeperformance of the steps described herein and as illustrated in FIG. 5.The controller 24 may comprise: control circuitry; and/or processorcircuitry; and/or at least one application specific integrated circuit(ASIC); and/or at least one field programmable gate array (FPGA); and/orsingle or multi-processor architectures; and/or sequential/parallelarchitectures; and/or at least one programmable logic controllers(PLCs); and/or at least one microprocessor; and/or at least onemicrocontroller; and/or a central processing unit (CPU); and/or agraphics processing unit (GPU), to perform the steps described hereinand as illustrated in FIG. 5.

In various examples, the controller 24 may comprise at least oneprocessor 25. Additionally or alternatively, the controller 24 maycomprise at least one memory (not shown). The memory may store acomputer program comprising computer readable instructions that, whenread by the processor 25, causes performance of the methods describedherein, and as illustrated in FIG. 5. The computer program may besoftware or firmware, or may be a combination of software and firmware.

The processor 25 may be located on the gas turbine engine 10, or may belocated remote from the gas turbine engine 10, or may be distributedbetween the gas turbine engine 10 and a location remote from the gasturbine engine 10. The processor 25 may include at least onemicroprocessor and may comprise a single core processor, may comprisemultiple processor cores (such as a dual core processor or a quad coreprocessor), for may comprise a plurality of processors (at least one ofwhich may comprise multiple processor cores).

The memory may be located on the gas turbine engine, or may be locatedremote from the gas turbine engine, or may be distributed between thegas turbine engine and a location remote from the gas turbine engine.The memory may be any suitable non-transitory computer readable storagemedium, data storage device or devices, and may comprise a hard diskand/or solid state memory (such as flash memory). The memory may bepermanent non-removable memory, or may be removable memory (such as auniversal serial bus (USB) flash drive or a secure digital card), Thememory may include; local memory employed during actual execution of thecomputer program; bulk storage; and cache memories which providetemporary storage of at least some computer readable or computer usableprogram code to reduce the number of times code may be retrieved frombulk storage during execution of the code.

The computer program may be stored on a non-transitory computer readablestorage medium. The computer program may be transferred from thenon-transitory computer readable storage medium to the memory. Thenon-transitory computer readable storage medium may be, for example, aUSB flash drive, a secure digital (SD) card, an optical disc (such as acompact disc (CD), a digital versatile disc (DVD) or a Blu-ray disc). Insome examples, the computer program may be transferred to the memory viaa wireless signal or via a wired signal.

It should be appreciated that the method illustrated in FIG. 5 may beperformed ‘offline’ on data which has been measured and recordedpreviously. Alternatively it may be performed in ‘real-time’, that is,substantially at the same time that the data is measured. In this case,the controller 24 may be coupled to the gas turbine engine 10 and may bean electronic engine controller or another on-board processor. Where thegas turbine engine 10 powers an aircraft, the controller 24 may be anengine controller, a processor on-board the gas turbine engine 10, or aprocessor on-board the aircraft.

Referring again to FIG. 2, a valve 40 and second sensor 42, also termedthe anti-icing sensor 42, are located within the bleed line 60, thevalve 40 comprising a valve actuator 63 for actuating between a firstposition and a second position. The valve 40 is arranged between thebleed line entry position, also known as a system source 43, and thecomponent entry position, also known as a system sink 44. The secondsensor 42 is located within the bleed line 60 downstream of the valve,between the valve 40 and the system sink 44. In further examples, thesecond sensor 42 is located within the manifold 61. Alternatively, twoor more second sensors 42 are located within the bleed line 60, at leastone second sensor being located within the bleed line 60 on either sideof the valve 40. in each case, each second sensor 42 provides pressuremeasurements to the system controller 24 so that the system controller24 interprets one or more of the pressure within the bleed line 60downstream of the valve 40, the pressure in an engine section statoranti-icing manifold 61 downstream of the valve 40, or the pressure deltaacross the valve 40 i.e. between the valve 40 and the component 62 to beheated. Additionally, multiple second sensors 42 could be used on one ormore sides of the valve 40 to provide greater data reliability and anindication of operational disparity, so indicating the operational stateof one or more sensors 42 by reference to one or more neighbouringsensors.

In some examples, the first position of the valve 40 represents an openposition and the second position represents a closed position, althoughalternate positions may be envisaged. The second sensor 42 is configuredto monitor the pressure within the bleed line 60 when the valve 40 is ina closed or at least partially open configuration. The valve 40 isconfigured to allow the fluid 64 to flow through the bleed line 60 fromthe system source 43 to the system sink 44 when the valve 40 is in anopen position. Conversely, the valve 40 is also configured to preventflow through the bleed line 60 when the valve 40 is in a closedposition. Thus, the valve 40 performs the function of turning theanti-icing system 23 on and off respectively

If the valve 40 fails open, one or more components 62 within or adjacentto the anti-icing system 23 are exposed to warm fluid 64 which can bedetrimental to the longevity of the components 62 included within theanti-icing system 23 or surrounding electrical components. Suchcomponents 62 may be susceptible to an increased likelihood of fatiguecrack growth and/or the occurrence of creep due to components beingsubjected to increased loading at high temperatures. The anti-icingvalve 40 failing open can also have a detrimental effect on theefficiency of particular operations or the overall specific fuelconsumption of the engine 10 due to the extraction of fluid 64 from thefluid flow when it is not required.

If the anti-icing valve 40 fails closed, the supply of fluid 64 to theone or more components 62 included within the anti-icing system 23 isinterrupted, meaning that the engine core is unprotected against iceformation. This may lead to one or more irregular operating conditionsincluding rollback (i.e. uncommanded reduction in thrust), engine surge,flameout, or damage to one or more further components located within theengine 10 as a result of ice entering the engine 10 core. Suchcomponents may include the intermediate pressure compressor 14 and highpressure compressor 15.

When the valve 40 is operational, an observed change or delta inpressure within the bleed line 60 when moving the valve 40 between afirst position and a second position confirms that the valve 40 ismoving following a command to do so. Thus, the observation of a pressuredelta by the second sensor 42 when moving the valve 40 between a firstand second position provides confirmation of valve function. The firstposition may be one of an open or closed position. The second positionmay be a closed or open position, depending on the respectiveconfiguration of the valve when in the first position. Thus, the firstor second position relates to the valve being fully open or fullyclosed, or any respective position therebetween. When testing the valve40 by cycling between an open and closed position, a lack of pressurechange detected by the valve 40 indicates that the valve 40 is stuck inone of an open, partly open, partly closed, or closed configuration, orthat the anti-icing system 23 is not operating correctly.

FIG. 3 shows a plot of fluid pressure within the bleed line 60 betweenthe valve and the system sink, as measured by the second sensor 42. Thisis plotted against the state of the valve on the x-axis, described asvalve open 55 a and valve closed 55 b. Here, the fluid pressure withinthe bleed line 60 between the valve and the system sink is also known asthe second pressure 55. As the test is carried out at ground idle engineconditions when operational engine 10 and ambient pressures are low, thepressure change to be measured is small. To avoid aliasing the signatureof the valve transition with other engine events, such as operation ofthe engine or dispatch of an aircraft, the test is aborted if the enginedeparts from steady state operation. Such departures from steady stateoperation can, in some instances, be provided by changes in bleed valve40 state or accessory power. Furthermore, at ambient or low-pressureconditions, an overlap 58 in second pressure 55 is shown in FIG. 3 wherethe valve 40 could be interpreted by the system controller 24 as beingeither open or closed. Such an overlap gives rise to uncertainty whendiagnosing valve 40 operability.

When at idle conditions, the small difference between system source 43and system sink 44 pressures is problematic when carrying out the testat different ambient conditions. Such variation may occur between highaltitude and low altitude airports where the difference in ambientconditions can alter the measured pressures by more than the pressuredelta ordinarily seen when actuating the valve 40. Thus, it is notpossible to determine whether the absence of a pressure change indicatesthat the valve 40 is stuck in an open or closed configuration. As thedispatch restrictions in either case differ, it is desirable to be ableto determine the state of the valve 40 following the test. The abilityto determine the state of the valve 40 allows determination of whetherthe valve 40 is stuck open or stuck closed. Thus, the state of the valveindicates whether the valve is closed or at least partially open whenthe valve is in either or both of the first position or second position.In some examples, the state of the valve may indicate whether the valveis closed, partially open or substantially open when the valve is ineither or both of the first position or second position, depending onthe sensitivity of the system.

Referring again to FIG. 2, the positioning of the second sensor 42downstream of the control valve 40 provides an improved signal withfewer sources of variation during normal use. However, a disadvantage oflocating the second sensor 42 downstream of the control valve 40 is thatthe measured change in second pressure 55 when the valve 40 is openand/or closed will be low, particularly when the engine is operating atidle conditions. Upstream of the valve 40, between the system source 43and the valve 40, the pressure within the bleed line 60 varies withsystem source 43 fluid pressure and may be affected by fluid offtakefrom the compressed fluid to drive external accessories. Suchaccessories can include hydraulics or further power systems which canchange demand without warning.

In addition to the second sensor 42, a first sensor 41 is located withinthe fluid flow entering the engine 10, the first sensor 41 beingconfigured to monitor the pressure within the fluid flow prior to thecompression stage. The first sensor 41 is preferably located remotely orindirectly within the fluid flow, such as in a bore hole or bleed linefluidly connected to the fluid flow entering the engine 10 prior to thecompression stage. The incorporation of a further parameter into thetest enables comparison of second pressure 55 with a first pressure 54obtained from the first sensor 41.

The first 54 and second 55 pressure values measured by or derived fromthe first sensor 41 and second sensor 42 respectively, are fed into thesystem controller 24 for comparison and/or further analysis. The firstsensor 41 provides data to the controller 24 in its actual state inorder to determine a first pressure value 54. Alternatively, data fromthe first sensor 41 can be used to determine the pressure of one or morefurther locations within the engine 10, the determined pressure of thefurther fluid flow describing the first pressure 54. Thus, the firstpressure 54 represents either an actual or derived value for pressurerepresenting a known or theoretical working condition within the engine10.

The first pressure 54 can be determined through calculation orderivation, or from one or more of a known initial pressure 53,temperature or volume. Additionally or alternatively, the values used tocalculate, derive or correlate the first pressure 54, such as theinitial pressure 53, can also be determined by respective sensors andassociated control systems. Thus, the first pressure 54 can be derivedusing, for example one or more of P20, LPC inlet total temperature T20,fan speed, fan geometry or fan configuration. Alternatively, the firstpressure 54 can be numerically derived from P20, T20 and fan speed usingone or more gas laws or equations associating pressure, temperature andvolume.

By comparing the second pressure 55 with the first pressure 54, the testdetermines whether the valve 40 is operational, that is cycling betweenopen and closed with a corresponding change in observed pressure.Alternatively, the test determines that the valve 40 is stuck, so as tonot cycle between a position which is perceived by the valve actuationsystem to be open or closed with little or no change in observedpressure. The test additionally determines whether the valve 40 is stuckin an open configuration, or stuck in a closed configuration.

As shown in FIG. 2, the first pressure 54 may be the IP compressor entryP24 pressure. By introducing the further parameter of first pressure 54into the test so that the controller compares the first 54 and second 55pressures, the test determines whether the valve 40 is closed, partiallyopen, and/or open according to one or more predetermined rules. Datagathered from engine testing shows that the pressure in the anti-icingsystem downstream of the control valve 40 is closely related to thepressure at the system sink, shown in FIG. 2 as P24.

According to a pre-determined condition, the valve 40 is determined tobe closed when the pressure observed by the second pressure sensor 42 isabout equal to the first pressure 54, plus or minus measurement error.The valve 40 is determined to be open when the pressure observed by thesecond pressure sensor 42 is equal to or greater than a detectionthreshold, also known as a success criterion. The detection thresholdrepresents a second pressure value that is greater than the firstpressure 54, plus or minus measurement error. Additionally, safetymargins can be used to define the detection threshold (by multiplyingthe second pressure 55 by a safety factor of at least 1) to determinewhether the second pressure 55 exceeds the first pressure 54 to anextent that measurement error can be excluded. Using safety margins, thevalve 40 can be determined to be in an open position when the secondpressure 55 observed by the second sensor 42 is about equal to or higherthan 1.01 times the first pressure 54. Alternatively, the valve 40 canbe determined to be in an open position when the second pressure 55observed by the second sensor 42 is about equal to or higher than 1.05times the first pressure 54. Alternatively, the valve 40 can bedetermined to be in an open position when the second pressure 55observed by the second sensor 42 is about equal to or higher than 1.08times the first pressure 54. Further safety factor multiplication valuesmay be alternatively or additionally used,

FIG. 4 shows a plot of second pressure 55 on the y-axis, against firstpressure 54 on the x-axis, FIG. 4 additionally shows plotted data trendsdefining the second pressure when the valve is closed 55 a, a detectionthreshold 59 with or without a safety factor, and the second pressurewhen the valve is open 55 b. Using a multiplication factor to multiplythe first pressure 54 before assessing the second pressure 55 againstthe first pressure 54 allows reduced sensitivity to temporaryfluctuations in pressure at the system source 43 and system sink 44.Temporary fluctuations in engine power can, in certain situations,confuse the anti-icing system 23 due to fluctuations in either the first54 or second 55 pressures. Such fluctuations can arise due to externalinfluences on the system source 43 and system sink 44 fluid pressures,Thus, the detection threshold 59 can alternatively comprise a value ofpressure added to or subtracted from the first pressure 54. Such valuescan include, for example, first pressure +0.3 psi, or similar.Alternatively, the value could increase or decrease depending on fluidpressures, temperatures or external events experienced within or aroundthe engine 10. Such a detection threshold 59 may be independent of, orin addition to, the multiplier of one or more of the first 54 and second55 pressures. Such a success detection threshold 59 could additionallyinclude the requirement of two or more successive and consistentpressure measurements to indicate a particular valve 40 condition.

Referring again to FIG. 2, warm fluid is fed into the component 62following compression, for example from the intermediate pressurecompressor compression stage 14, The second pressure 55 is greater thanthe operational pressure at the exit of the component 62 (i.e. thesystem sink 44 pressure in the region where the anti-icing system 23exhausts) when the valve is open. Alternatively, the second pressure 55is equal to or less than the operational pressure at the exit of thecomponent 62 (i.e. the system sink pressure in the region where theanti-icing system 23 exhausts) when the valve 40 is closed. Additionallyor alternatively, second pressure 55 is less than or equal to theoperational pressure at the system source 43 when the valve is open.

The controller 24, in conjunction with the anti-icing system 23, canadditionally track the time taken for the valve 40 to switch fromconfirmed closed position to a confirmed open position, or vice versa.Such a time period can be identified by monitoring the delta in secondpressure 55 along with the time period taken for the valve 40 toactuate. The controller 24 can, additionally or alternatively, advise ofa deteriorating valve 40 by monitoring the second pressure 55 againstvalve status, that is the reported position of the valve 40. Earlyidentification of a deteriorating valve 40, aids in the prevention ofoperational disruption due to unplanned repair. Additionally oralternatively, the system 23 can also monitor the time taken for thevalve to move from the first position to the second position, somonitoring the time taken for the determined state to match thecommanded state of the valve 40. If the time taken for the determinedstate to match the commanded state is greater than a pre-determined timethreshold, the test may additionally provide an indication or warning ofvalve failure,

Changes in the pressure within the bleed line 60 between the valve 40and the component 62 arising due to changes in an engine operatingcondition can also be corrected by the controller 24. Such a correctionis accomplished by checking or comparing the first pressure 54 againstthe second pressure 55. Incorporation of the additional check of thefirst 54 and second 55 pressure within the anti-icing system removes therequirement to abort the valve 40 state check when observing changes inengine 10 or operating conditions. Incorporation of the additional checkof the first 54 and second 55 pressure within the anti-icing system 23allows the valve 40 status to be detected prior to dispatch of theaircraft. This allows valve 40 status to be advantageously determined asa pre-flight check.

FIG. 5 illustrates a flow diagram of steps according to variousexamples, wherein:

At block 70, the system determines the first pressure 54 of a fluid flowat a first location within the engine 10. The first pressure 54 isobtained from the first sensor 41, the first pressure 54 representing anactual, calculated, derived or determined value from one or more ofknown pressures, temperatures and volumes within the engine 10. Thus,the first pressure 54 can be derived using one or more gas laws orequations associating pressure, temperature and volume.

At block 71, the system determines a second pressure 55 of a fluid at asecond location within a bleed line located within the engine 10 whenthe valve is in the first position. The second pressure 55 isrepresentative of the pressure within the bleed line 60 as determined byone or more pressure sensors 42 between the valve 40 and the system sink44 and/or one or more pressure sensors 42 between the valve 40 and thesystem source 43. Where one or more sensors 42 are located on eitherside of the valve 40, the second pressure sensor 42 can measure thesecond pressure 55 delta across the valve 40, within the bleed line 60,or within the anti-icing manifold 61. Where one or more sensors 42 arelocated between the valve 40 and the system sink 44 only, the secondpressure sensor 42 can measure the second pressure 55 within the bleedline 60, or within the anti-icing manifold 61, depending on sensor 42locations.

At block 72, the system compares the first pressure 54 and the secondpressure 55. In this step, by comparing the second pressure 55 observedby the second sensor 42 with the first pressure 54 observed by the firstsensor 41, the test determines whether there is any difference or deltabetween the first pressure 54 and the second pressure 55 when the valve40 is in the first position.

At block 73, the system determines the state of the valve 40. In thisstep, the test determines whether the second pressure 55 is equal to,greater than, or less than the first pressure 54 to determine the stateof the valve. Where the second pressure 55 is equal to or less than thepressure at the system sink 44, the valve is determined to be closed.Conversely, the valve 40 is determined to be at least partially openwhen the second pressure 55 is at least partially greater than the firstpressure 54 to the extent that measurement error can be excluded.

Further optional steps of the system follow.

In addition to the step described at block 73, the system can alsomonitor the time taken for the valve to move from the first position tothe second position, providing an indication or warning of valvefailure.

At block 74, the system commands the valve 40 to move from the firstposition towards a second position. In this step, the system 23 and/orcontroller 24 commands the valve 40 to move from the first positiontowards the second position by actuation of the valve actuator 63. Thefirst and second positions relate to closed and open positionsrespectively. However, the first and second positions couldalternatively relate to any position between an open and closed positionas required by the anti-icing system 23. Alternatively, the first andsecond positions could relate to open and closed positions respectively,or any position between an open and closed position as required by theanti-icing system 23.

At block 75, the system determines the second pressure 55 of thecompressed fluid at the second location when the valve 40 has beencommanded towards the second position. In this step, step 71 is repeatedto determine the second pressure 55 when the valve 40 has been commandedto move towards the second position. The one or more second pressuresensors 42 communicate the second pressure 55 to the system controller24 for comparison and/or further analysis.

At block 76, the system compares the pressure at the second locationwhen the valve 40 is in the first position to the pressure at the secondlocation when the valve 40 has been commanded to move towards the secondposition. In this step, comparing the second pressure 55 when the valve40 has been commanded to move towards the second position allows thetest to determine whether there is any difference or delta between thesecond pressure 55 when the valve 40 is in the first position and whenthe valve 40 is in the second position.

At block 77, the system determines whether the valve 40 has moved fromthe first position towards the second position when commanded to do so.In this step, monitoring the second pressure 55 allows the system 23 tomonitor pressure changes within the bleed line 60 when cycling the valve40 between a first and second position, or vice versa. The observationof a pressure change, or delta, by the second sensor 42 following acommand to move the valve 40 from a first position to a second positionprovides a confirmation of valve 40 function.

By comparing the second pressure 55 when cycling between a first andsecond position with the first pressure 54, the test determines whetherthe valve 40 is operational, that is cycling between open and closedwith a corresponding change in observed pressure. Alternatively, thetest determines that the valve 40 is stuck, that is in a single positionwhich is perceived by the valve actuation system to be open or closedwith little or no change in observed pressure, or change in observedpressure difference. The test additionally determines whether the valve40 is stuck in an open configuration, or stuck in a closedconfiguration.

If the test determines that the valve 40 is operational, that is cyclingbetween a position which is perceived by the system 23 to be open andclosed with an identifiable change in observed pressure, the systemloops back to step 70 for the following check.

At block 78, the system provides an alert if no change in pressure, andthus no change of valve 40 state, is detected. In this step, an alert isprovided if the change in second pressure 55 does not meet the requireddetection threshold 59. A change in second pressure 55 which does notmeet the required detection threshold 59 indicates that the valve 40 hasnot moved from the first position to the second position as intended. Inthis way, the system provides a diagnosis of a faulty valve 40 containedwithin the anti-icing system 23.

The steps conducted by the system as described in FIG. 5 are conducted‘online’, where data from the components included as part of the systemis fed into the controller 24 and/or system 23 by wired electrical, orwireless electromagnetic connection for further analysis. Alternativearrangements may be provided where the steps conducted by the systemillustrated in FIG. 5 are performed ‘offline’ on data which has beenmeasured and recorded previously, or sent via a data link to an externalcontroller 24 and/or system 23. In either case, the analysis and controlof the system 23 is performed in ‘real-time’, that is, substantially atthe same time that the data is measured. In this case, the controller 24is coupled to the engine 10 and can be an electronic engine controller31 or another on-board processor. Where the engine 10 powers anaircraft, the controller 24 could be included as part of an enginecontroller 31, a processor on-board the engine 10, or a processoron-board the aircraft itself.

It will be understood that the invention is not limited to theembodiments above-described and various modifications and improvementscan be made without departing from the concepts described herein.

Except where mutually exclusive, any of the features may be employedseparately or in combination with any other features and the disclosureextends to and includes all combinations and sub-combinations of one ormore features described herein.

1. A system to determine a state of a valve, the system comprising acontroller configured to: a) determine a first pressure of a fluid flowat a first location within a gas turbine engine; b) determine a secondpressure of a compressed fluid at a second location within the gasturbine engine when the valve is in the first position; c) compare thefirst pressure and the second pressure to determine the state of thevalve. d) command the valve to move from the first position towards asecond position; e) determine the second pressure of the compressedfluid at the second location; f) compare the pressure at the secondlocation when the valve is in the first position to the pressure at thesecond location when the valve has been commanded to move towards thesecond position; and, g) determine whether the valve has moved from thefirst position towards the second position when commanded to do so.
 2. Asystem as claimed in claim 1, wherein the second location comprises ableed line.
 3. A system as claimed in claim 2, step 1f) furthercomprising a step to determine a change in pressure within the bleedline.
 4. A system as claimed in claim 3, the system being configured todeclare a fault condition if the change in pressure within the bleedline is about zero.
 5. A system as claimed in claim 3, the system beingconfigured to declare a fault condition if a change in pressuredifference between the pressure at the first location and the pressureat the second location is about zero.
 6. A system as claimed in claim 1,step 1a), the controller being additionally configured to: a) measure aninitial fluid pressure at a third location within a gas turbine engine;and, b) determine the first pressure from the initial fluid pressure. 7.A system as claimed in claim 2, the bleed line being configured toextend from a compressor exit flow to a component.
 8. A system asclaimed in claim 1, the system comprising a first sensor within a fluidflow at a first location within a gas turbine engine configured tomeasure the first pressure, the first sensor being in communication withthe controller.
 9. A system as claimed in claim 8, the system comprisinga second sensor at a second location within the gas turbine engineconfigured to measure the pressure at the second location, the secondsensor being in communication with the controller.
 10. A system asclaimed in claim 1, the controller being configured to declare a faultcondition if a difference between the pressure at the second locationwhen the valve is in a first position and when the valve is in a secondposition is about zero.
 11. A system as claimed in claim 1, thecontroller being configured to declare a fault condition if a change inpressure difference between the pressure at the first location and thepressure at the second location is about zero.
 12. A system as claimedin claim 1, the controller being configured to determine the firstpressure from an initial fluid pressure at a third location within thegas turbine engine.
 13. A system to determine a state of a valve asclaimed in claim 2, the bleed line being configured to extend from acompressor exit flow to a component.
 14. A gas turbine enginecomprising: a bleed line; a valve within the bleed line to control flowtherethrough; a first pressure sensor within the gas turbine engine; asecond pressure sensor within the bleed line; and, a controllerconfigured to receive a first pressure reading from the first pressuresensor and a second pressure reading from the second pressure sensor,the controller being configured to perform the steps claimed in claim 1.15. A system to determine a state of a valve, the system comprising acontroller comprising a processor, the processor being configured tofunction as a determining module to make a comparison between valuesand: a) determine a first pressure of a fluid flow at a first locationwithin a gas turbine engine; b) determine a second pressure of acompressed fluid at a second location within the gas turbine engine whenthe valve is in the first position; c) compare the first pressure andthe second pressure to determine the state of the valve; d) command thevalve to move from the first position towards a second position; e)determine the second pressure of the compressed fluid at the secondlocation; f) compare the pressure at the second location when the valveis in the first position to the pressure at the second location when thevalve has been commanded to move towards the second position; and, g)determine whether the valve has moved from the first position towardsthe second position when commanded to do so.
 16. A method to determine astate of a valve, the method comprising steps to: a) determine a firstpressure of a fluid flow at a first location within a gas turbineengine; b) determine a second pressure of a compressed fluid at a secondlocation within the gas turbine engine when the valve is in the firstposition; c) compare the first pressure and the second pressure todetermine the state of the valve; d) command the valve to move from thefirst position towards a second position; e) determine the secondpressure of the compressed fluid at the second location; f) compare thepressure at the second location when the valve is in the first positionto the pressure at the second location when the valve has been commandedto move towards the second position; and, g) determine whether the valvehas moved from the first position towards the second position whencommanded to do so.